Method for producing metal formed article

ABSTRACT

There is disclosed a method for producing a metal formed article having a space in the interior thereof, comprising the steps of laying a formed article  2   a  of a second metal in a powder  1  containing a first metal to thereby form a powder formed article  3   a  and heating and melting the formed article  2   a  at a temperature less than a melting point of the first metal and not less than that of the second metal to form a space  4 . Both the metals are sintered and solidified. A coating layer  6  is formed on the space  4  by an intermetallic compound or an alloy of both the metals. When the coating layer  6  is the intermetallic compound, the first metal is one type of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Hf, Ta, and W and an alloy of these elements, and the second metal is Al. The first metal is Ti, V, Cr, Fe, Co, Ni, Zr, Nb, Mo, Hf, Ta, and W and an alloy of these elements, and the second metal is Si. The first metal is Cu or an alloy thereof, and the second metal is Sn. When the coating layer  6  is the alloy, the first metal is Al or an alloy thereof, and the second metal is Zn.

TECHNICAL FIELD

The present invention relates to a method for producing a metal formed article having a micro space in the interior thereof.

BACKGROUND ART

There has been a mold having a pipe line to circulate a medium to be cooled or heated in the interior thereof as a mold for use in injection molding of plastic, casting of a metal and the like.

As in the above-described mold or the like, a metal formed article having a space such as a pipe line in the interior thereof as described above has heretofore been formed by a metal injection molding or precision casting method. However, since either of the above-described methods is a producing method using the mold itself, there are restrictions as to a shape and size of the formable space, and there is a disadvantage that it is difficult to form a space having a complicated shape or a micro space.

On the other hand, a method has been known in which a first metal material is disposed on a substrate metal, a second metal material having a melting point higher than that of the first metal material is thermally sprayed on the substrate metal and the first metal material to form a sprayed metal layer, thereafter the first metal material is heated and dissolved at a temperature lower than the melting point of the second metal material, and a composite metal article having a space portion corresponding to a first metal shape is produced (Japanese Laid-Open Patent Publication No. 11-279274).

However, in the above-described method, since a layer of the second metal material formed on the first metal material is formed by the thermal spraying, there is a disadvantage that a large energy and a long time are required in order to form the layer having a predetermined thickness.

[Patent Document 1]

Japanese Laid-Open Patent Publication No. 11-279274

[Patent Document 2]

Japanese Laid-Open Patent Publication

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a method capable of solving such disadvantage and easily producing a metal formed article having a space having a complicated shape or a micro space in the interior thereof.

To achieve the object, according to the present invention, there is provided a method for producing a metal formed article, comprising the steps of burying a formed article comprising a second metal whose melting point is lower than that of a first metal in a powder containing the first metal, and forming a powder formed article containing the formed article, and heating the powder formed article at a temperature lower than the melting point of the first metal and higher than the melting point of the second metal, melting the second metal, allowing the molten second metal to move into voids in the powder containing the first metal, forming a space in a region which has been occupied by the formed article comprising the second metal, and sintering and solidifying the powder of the first metal and the molten second metal.

In the method for producing the metal formed article of the present invention, first the formed article comprising the second metal whose melting point is lower than that of the first metal is buried in the powder containing the first metal. The powder may contain not only the powder of the first metal but also a powder of a binder, another metal, ceramic or the like.

There is no restriction as to a size of the formed article comprising the second metal, and the article may be a linear material having a micro diameter, a rod material or the like. There is no restriction as to a shape of the formed article comprising the second metal. For example, when the linear material or the rod material is used, the shape is not limited to a straight line shape, and any shape may be used such as a curved line, bent meander shape or the like.

Next, the powder formed article is formed from the powder containing the first metal. At this time, the formed article comprising the second metal is included inside the powder formed article in a buried state in the powder of the first metal. The powder formed article may be subjected to a preliminary pressurizing process, and the formed article comprising the second metal may be shaped by the preliminary pressurizing process if necessary.

Next, the powder formed article is heated at the temperature which is lower than the melting point of the first metal and higher than the melting point of the second metal. In this case, the second metal is melted, and the molten second metal moves between particles of the powder of the powder formed article containing the first metal. As a result, the space is formed in the region which has been occupied by the formed article comprising the second metal.

Then, next the powder of the first metal and the molten second metal are sintered and solidified, and accordingly the metal formed article having the space in the interior thereof can be obtained.

According to the method for producing the metal formed article of the present invention, the formed article comprising the second metal buried beforehand in the powder containing the first metal to thereby form the space in the region which has been occupied by the formed article comprising the second metal. Therefore, the metal formed article having a space having a complicated shape such as a small chamber or a pipe line, or a micro space can be easily produced.

Moreover, the method for producing the metal formed article of the present invention further comprises the step of forming a coating layer to coat the surface of the space formed in the region which has been occupied by the second metal by an intermetallic compound or an alloy formed of the first and second metals.

A method has heretofore been known in which a mixed metal powder forming the intermetallic compound by a reaction is applied onto the surface of the metal material and heated, and accordingly a coating layer comprising the intermetallic compound prepared from the mixed metal powder is formed on the surface of the metal material (see Japanese Laid-Open Patent Publication No. 10-219474). However, in this method, it is difficult to form the coating layer comprising the intermetallic compound on the surface of the space formed inside the metal formed article.

In this respect, according to the method for producing the metal formed article of the present invention, the formed article comprising the second metal buried in the powder containing the first metal can be molten and moved among particles of the powder containing the first metal. Therefore, the intermetallic compound or the alloy is prepared by the first and second metals, and accordingly the coating layer comprising the intermetallic compound or the alloy can be easily formed on the surface of the space formed in the region which has been occupied by the second metal.

At this time, when there are voids permeable to the molten second metal among the particles of the powder containing the first metal, and the particles of the powder containing the first metal are easily wetted by the molten second metal, the molten second metal spontaneously and quickly permeates among the particles of the powder containing the first metal by a capillary phenomenon. On the other hand, when there are no voids permeable to the molten second metal among the particles of the powder containing the first metal, the molten second metal moves only by diffusion.

Therefore, when a void ratio among the particles of the powder containing the first metal is adjusted beforehand, a permeation speed of the molten second metal or a permeating depth can be controlled, and thickness of the coating layer comprising the intermetallic compound or the alloy can be freely controlled.

To form the coating layer comprising the intermetallic compound, one type of metal selected from a group consisting of transition metals such as Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Hf, Ta, and W and an alloy of these elements is usable as the first metal, and Al is usable as the second metal. In this case, various transition metal aluminide is prepared as the intermetallic compound.

Moreover, to form the coating layer comprising the intermetallic compound, one type of metal selected from a group consisting of transition metals such as Ti, V, Cr, Fe, Co, Ni, Zr, Nb, Mo, Hf, Ta, and W and an alloy of these elements is usable as the first metal, and Si is usable as the second metal. In this case, various transition metal silicide is prepared as the intermetallic compound.

Furthermore, to form the coating layer comprising the intermetallic compound, Cu or an alloy of this element is used as the first metal, and Sn may be used as the second metal.

On the other hand, to form the coating layer comprising the alloy, Al or an alloy of this element is usable as the first metal, and Zn or an alloy of this element is usable as the second metal.

In the producing method of the present invention, the powder formed article is preferably heated to at least the melting point of the second metal at a temperature rising rate of 1 kelvin/second or more especially in a case where the formed article of the second metal comprises a micro portion. In this case, a continuous space can be securely formed in the region which has been occupied by the formed article comprising the second metal. When the temperature rising rate in heating the powder formed article to at least the melting point of the second metal is less than 1 kelvin/second, any continuous space is not formed in the region which has been occupied by the formed article comprising the second metal in some case.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing one embodiment of a producing method of the present invention;

FIG. 2 is a sectional view along line II-II of FIG. 1;

FIG. 3 is a perspective view showing one embodiment of the producing method of the present invention;

FIG. 4 is a sectional view along line IV-IV of FIG. 3;

FIG. 5 is a perspective view showing one embodiment of the producing method of the present invention; and

FIG. 6 is a sectional view along line VI-VI of FIG. 5.

BEST MODE FOR CARRYING OUT THE INVENTION

Next, a mode for carrying out the present invention will be described in more detail with reference to the accompanying drawings. FIGS. 1 to 6 are explanatory views of a method for producing a metal formed article of the present embodiment.

In the method for producing the metal formed article of the present embodiment, first as shown in FIG. 1, a linear material 2 comprising a second metal whose melting point is lower than that of a first metal is buried in a powder 1 comprising a first metal to form a preliminary formed article 3. For example, the linear material 2 may have a rectangular sectional shape shown, for example, in FIG. 2, or a circular sectional shape.

Next, the preliminary formed article 3 is preliminarily uniaxially compressed along a length direction of the linear material 2. As a result, as shown in FIGS. 3 and 4, the linear material 2 is shaped, and a powder formed article 3 a is obtained in which a linear material 2 a having an elliptic sectional shape is formed.

Next, the powder formed article 3 a is heated at a temperature lower than the melting point of the first metal and higher than the melting point of the second metal using a heating device for use in general powder metallurgy. In this case, the linear material 2 a comprising the second metal shown in FIGS. 3 and 4 is molten, and permeates in the powder 1 comprising the first metal. Moreover, the powder 1 and the molten second metal are sintered and solidified. The powder formed article 3 a is preferably heated to at least the melting point of the second metal at a temperature rising rate of 1 kelvin/second or more in order to form a continuous space in a region which has been occupied by the linear material 2 a.

As a result, as shown in FIGS. 5 and 6, a metal formed article 5 is obtained having a space 4 having the same fine tubular shape as that of the linear material 2 a in a region which has been occupied by the linear material 2 a. In the metal formed article 5, a coating layer 6 comprising an intermetallic compound or an alloy of the first and second metals is formed on the surface of the space 4.

In the present embodiment, a case where the fine tubular space 4 having the elliptic sectional shape is formed by the linear material 2 a having a straight line shape has been described, but the linear material 2 a may have any shape such as a curved line shape or a bent meander shape, or a formed article having a lump shape may be used instead of the linear material 2 a.

When the linear material 2 a having the above-described various shapes is used, the fine tubular space 4 may be formed into the straight line shape, curved line shape, bent meander shape or the like, and a pipe line can be formed by the space 4. By the use of the lump-shaped formed article instead of the linear material 2 a, a small chamber can be formed. Moreover, when the pipe line is combined with the small chamber, the space 4 having a further complicated shape can be formed.

Therefore, the producing method of the present invention is usable, for example, for forming a pipe line in which a cooling or heating medium circulates inside a mold for use in injection molding of plastic or casting of a metal, and a high degree of freedom can be obtained in designing the pipe line in order to optimize temperature control.

Moreover, according to the producing method of the present invention, since the coating layer 6 comprising the intermetallic compound or the alloy can be formed on the surface of the space 4, it is expected that the obtained metal formed article 5 can be used in many applications.

It is to be noted that in the above-described embodiment, the powder 1 formed of the first metal is used, but the powder 1 may contain a powder of a binder, another metal, ceramic or the like.

When the coating layer 6 comprising the intermetallic compound is formed on the surface of the space 4 in the above-described embodiment, a powder comprising one type of metal selected from a group consisting of Ni, Ti, V, Cr, Mn, Fe, Co, Cu, Zr, Nb, Mo, Hf, Ta, and W and an alloy of these elements is used as the first metal, and Al is used as the second metal. Alternatively, one type of metal selected from a group consisting of Ti, V, Cr, Fe, Co, Ni, Zr, Nb, Mo, Hf, Ta, and W and an alloy of these elements is used as the first metal, and Si is used as the second metal. Furthermore, Cu or an alloy of this element is used as the first metal, and Sn may be used as the second metal.

Moreover, when the coating layer 6 comprising the alloy is formed on the surface of the space 4 in the above-described embodiment, Al or an alloy of this element is used as the first metal, and Zn or an alloy of this element is used as the second metal.

Next, examples will be described.

EXAMPLE 1

In the present example, as shown in FIG. 1, an aluminum linear material 2 was buried in a nickel powder 1, and a preliminary formed article 3 was formed using nickel (m. p. 1528 K) as a first metal and aluminum (m. p. 933 K) as a second metal. The aluminum linear material 2 has a rectangular sectional shape whose long side has a length of 0.70 mm and whose short side has a length of 0.45 mm.

Next, the preliminary formed article 3 was preliminarily uniaxially compressed along a length direction of the linear material 2. As a result, as shown in FIGS. 3 and 4, a powder formed article 3 a was obtained in which a linear material 2 a having an elliptic sectional shape with a long diameter of 1.20 mm and a short diameter of 0.35 mm was formed.

Next, the powder formed article 3 a was heated at a temperature of 1273 K lower than the melting point of nickel and higher than the melting point of aluminum for one hour using a heating device for use in general powder metallurgy. As a result, the linear material 2 a was molten to permeate the nickel powder 1, moreover the nickel powder 1 and molten aluminum were sintered and solidified, and as shown in FIGS. 5 and 6, a metal formed article 5 was obtained having a space 4 having the same fine tubular shape as that of the linear material 2 a in a region which had been occupied by the linear material 2 a. In the metal formed article 5, a coating layer 6 comprising nickel aluminide which was an intermetallic compound of nickel and aluminum was formed on the surface of the space 4.

EXAMPLE 2

In the present example, aluminum linear materials 2 having circular sectional shapes with diameters of 50 μm, 100 μm, 200 μm, 500 μm were buried as a second metal in a nickel powder 1 which was a first metal, and four types of preliminary formed articles 3 were formed. Next, the respective preliminary formed articles 3 were preliminarily uniaxially compressed along length directions of the linear materials 2 at a pressure of about 600 MPa, and powder formed articles 3 a were formed.

Next, the respective powder formed articles 3 a were heated using a heating device for use in general powder metallurgy. The articles were heated at 983 K at a temperature rising rate of 2 kelvin/second, the aluminum linear materials 2 were molten in a short time, further heated at 1473 K at a temperature rising rate of 0.2 kelvin/second, and thereafter cooled at room temperature at a cooling rate of 0.4 kelvin/second, and four types of metal formed articles 5 were produced. In each of the respective metal formed articles 5, a continuous space 4 having the same fine tubular shape as that of a linear material 2 a was formed in a region which had been occupied by the linear material 2 a.

EXAMPLE 3

In the present example, four types of metal formed articles 5 were produced in the same manner as in Example 2 except that iron was used as a first metal. In each of the respective metal formed articles 5, a continuous space 4 having the same fine tubular shape as that of a linear material 2 a was formed in a region which had been occupied by the linear material 2 a.

EXAMPLE 4

In the present example, four types of metal formed articles 5 were produced in the same manner as in Example 2 except that titanium was used as a first metal. In each of the respective metal formed articles 5, a continuous space 4 having the same fine tubular shape as that of a linear material 2 a was formed in a region which had been occupied by the linear material 2 a.

EXAMPLE 5

In the present example, four types of metal formed articles 5 were produced in the same manner as in Example 2 except that stainless steel (SUS304) was used as a first metal. In each of the respective metal formed articles 5, a continuous space 4 having the same fine tubular shape as that of a linear material 2 a was formed in a region which had been occupied by the linear material 2 a.

It is apparent from Examples 2 to 5 that the powder formed article 3 a is heated exceeding the melting point of aluminum at a temperature rising rate of 2 kelvin/second which is not less than 1 kelvin/second, and accordingly the continuous space 4 can be formed, when the diameter of the aluminum linear material 2 was in a range of 50 to 500 μm.

EXAMPLE 6

In the present example, four types of metal formed articles 5 were produced in the same manner as in Example 2 except that a powder formed article 3 a was heated at 1473 K at a temperature rising rate of 0.2 kelvin/second, and thereafter cooled at room temperature at a cooling rate of 0.4 kelvin/second.

In the metal formed articles 5 using aluminum linear materials 2 having a diameter of 50 μm, a space 4 having the same fine tubular shape as that of a linear material 2 a and partially including a discontinuous portion was formed in a region which had been occupied by the linear material 2 a, but a continuous space 4 was formed in each of the other metal formed articles 5.

EXAMPLE 7

In the present example, four types of metal formed articles 5 were produced in the same manner as in Example 6 except that iron was used as a first metal.

In metal formed articles 5 using aluminum linear materials 2 having a diameter of 50 μm, a space 4 having the same fine tubular shape as that of a linear material 2 a and partially including a discontinuous portion was formed in a region which had been occupied by the linear material 2 a, but a continuous space 4 was formed in each of the other metal formed articles 5.

It is apparent from Examples 6, 7 that in a case where the first metal is nickel or iron, even when the powder formed article 3 a is heated at a temperature rising rate of 0.2 kelvin/second which is less than 1 kelvin/second, the space 4 can be formed in the region which has been occupied by the linear material 2 a. It is also apparent that in a case where the aluminum linear material 2 has a diameter in a range of 100 to 500 μm, even when the powder formed article 3 a is heated at a temperature rising rate of 0.2 kelvin/second which is less than 1 kelvin/second, the continuous space 4 can be formed.

EXAMPLE 8

In the present example, four types of metal formed articles 5 were produced in the same manner as in Example 6 except that titanium was used as a first metal. In each of the metal formed articles 5, a continuous space 4 having the same fine tubular shape as that of a linear material 2 a was formed in a region which had been occupied by the linear material 2 a.

EXAMPLE 9

In the present example, four types of metal formed articles 5 were produced in the same manner as in Example 6 except that stainless steel (SUS304) was used as a first metal. In each of the metal formed articles 5, a continuous space 4 having the same fine tubular shape as that of a linear material 2 a was formed in a region which had been occupied by the linear material 2 a.

It is apparent from Examples 8, 9 that in a case where the first metal is titanium or stainless steel, even when the powder formed article 3 a is heated at a temperature rising rate of 0.2 kelvin/second which is less than 1 kelvin/second, the continuous space 4 can be formed in the range of the diameter of the aluminum linear material 2 of 50 to 500 μm.

EXAMPLE 10

In the present example, a zinc (m. p. 692 K) linear material 2 having a circular sectional shape with a diameter of 500 μm was buried as a second metal in an aluminum powder 1 which was a first metal, and a preliminary formed article 3 was formed. Next, the preliminary formed article 3 was preliminarily uniaxially compressed along a length direction of linear material 2 at a pressure of about 800 MPa, and a powder formed article 3 a was formed.

Next, each powder formed article 3 a was heated using a heating device for use in general powder metallurgy. The article was heated at 773 K at a temperature rising rate of 0.2 kelvin/second, thereafter cooled at room temperature at a cooling rate of 0.4 kelvin/second, and a metal formed article 5 was produced. In each of metal formed articles 5, a continuous space 4 having the same fine tubular shape as that of a linear material 2 a was formed in a region which had been occupied by the linear material 2 a. In the metal formed article 5, a coating layer 6 comprising an Al—Zn alloy was formed on the surface of the space 4.

INDUSTRIAL APPLICABILITY

The present invention can be utilized in producing a metal formed article having space such as a pipe line to circulate a cooling or heating medium in the interior thereof, such as a mold for use in injection molding of plastic, casting of a metal and the like. 

1. A method for producing a metal formed article, comprising the steps of: burying a formed article comprising a second metal whose melting point is lower than that of the first metal in a powder containing a first metal, and forming a powder formed article containing the formed article; and heating the powder formed article at a temperature lower than the melting point of the first metal and higher than the melting point of the second metal, melting the second metal, allowing the molten second metal to move into voids in the powder containing the first metal, forming a space in a region which has been occupied by the formed article comprising the second metal, and sintering and solidifying the powder of the first metal and the molten second metal.
 2. The method for producing the metal formed article according to claim 1, comprising the step of forming a coating layer to coat the surface of the space formed in the region which has been occupied by the second metal by an intermetallic compound formed of the first and second metals.
 3. The method for producing the metal formed article according to claim 2, wherein the first metal is one type of metal selected from a group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Hf, Ta, and W and an alloy of these elements, and the second metal is Al.
 4. The method for producing the metal formed article according to claim 2, wherein the first metal is one type of metal selected from a group consisting of Ti, V, Cr, Fe, Co, Ni, Zr, Nb, Mo, Hf, Ta, and W and an alloy of these elements, and the second metal is Si.
 5. The method for producing the metal formed article according to claim 2, wherein the first metal is Cu or an alloy thereof, and a second metal is Sn.
 6. The method for producing the metal formed article according to claim 1, comprising the step of forming a coating layer to coat the surface of the space formed in the region which has been occupied by the second metal by an alloy formed of the first and second metals.
 7. The method for producing the metal formed article according to claim 6, wherein the first metal is Al or an alloy thereof, and the second metal is Zn or an alloy thereof.
 8. The method for producing the metal formed article according to any one of claims 1 to 7, wherein the powder formed article is heated to at least a melting point of the second metal at a temperature rising rate of 1 kelvin/second or more. 